"The first thing I said when I walked out after [my conversation with] Brooks was, 'We might be done.' We were in the home stretch trying to set up a happy ending and magic proposal. This was a curveball," host Chris Harrison said during a press call Thursday.

"The entire show was dumped upside down in the final two weeks of shooting. The beauty of our show, and the scariest thing, is that we take our hands off the wheel. It's up to the woman making the choices. Des needed to figure out if she wanted to continue or just pack up her bags and be done."

Read on for Harrison's other teases and thoughts on what creator Mike Fleiss is calling "the weirdest ending" in franchise history.

Throughout the seasons people have quit, fought, rejected both finalists, had secret girlfriends and many other dramatic things. Where did this ending rate in terms of shocking?

It's a one-of-a-kind situation. I can't remember anything happening this late in the game [that was] this devastating to our bachelor/bachelorette. I think she felt Brooks would be the guy and [him] pulling himself out crushed her.

There were red flags that something was a little off and that she was much further along than he was. Needing a silly game to express feelings [at their age] was a red flag.

At some point, three of the final four had professed their love. I kept bringing up [that Brooks hadn't] and she kept reassuring me that he would affirm his feelings in other ways. I took her word that she was sure about him. But no way did I think this was going to happen.

It was brutal to watch and guessing even more brutal to witness in person. What happened next?

We let her sit alone for 15 minutes on the pier to decompress and then I did go out there. We had another chat at her house after giving her time to pull herself together, which is where we'll pick up [in part two].

I went in because she needed [someone] to talk [to] and have somebody listen to where she was and what she wanted to do.

During the breakup, she told him she loved him and he asked why she hadn't told him earlier. Would it have changed anything?

I don't think it would have made any difference whatsoever if she had been on one knee begging for his hand in marriage weeks ago. His mind was made up when he went to see his family. He was looking for reassurance. [Saying that] was a defense mechanism and he was trying to be a good guy during the breakup.

Anybody could see Des was falling for this guy so unless he completely misread every signal she put out, it was a little bit of a cop out. But nothing you say or do makes you look good at that moment because you're breaking someone's heart.

He cares for Des. The fact that he left the show doesn't mean he dislikes or hates Des. He didn't do this with malice or ill intent. He was very sincere and torn when I talked to him. He had done his due diligence and talked it out with his family. He just knew that he wasn't at the point where he wanted to be with this woman.

I would have been disappointed and upset with him if he had stayed, had a fake proposal and gone out for a few weeks [before] breaking up. So Brooks did the right thing.

Did you sense any hesitation? Was it more about needing more time or being scared of proposal?

He had a really tough time articulating to me what he was thinking and I couldn't understand what he wanted to do. I found that very peculiar. I kept having to treat him like a hostile witness.

I thought maybe he didn't want to leave or needed more time, [like] he was looking for a way out almost [as much] as a way to stay in. I made it clear there is no pressure and a ton of options beyond a proposal.

I don't know if he was a 100 percent but he has a history of not quite being able to commit.

Can you tease what happens next week?

Part of the problem we have to solve in the finale is that we have two happy guys, Chris and Drew, who are head over heels in love with her and who have no idea that [Desiree] just had her world rocked.

It may not be much of anything next week other than her talking and saying goodbye to the other two.

It's absolutely possible for him to come back in the game. She may be open to it or maybe she learned her lesson and he's not the guy anymore.

She admitted that she loved Brooks weeks earlier and told him he was the one she wanted to be with during the breakup. If she still picks Drew or Chris, won't that look like settling?

[After] she said that in Munich, she also said she loves Chris in the next sentence and then that she was falling in love with Drew in the next. Everyone really picked up the Brooks thing and forgot what she said about the other guys.

You saw Des at the Men Tell All taping two weeks ago. How is she coping now?

Des – and I'm assuming this comes from the way she grew up – is a survivor. She put herself out there and allowed herself to be vulnerable [knowing there was] a good chance she could get hurt like that.

You'll have to watch what happens next week, [but] he obviously has trouble committing and although he was sincere in coming on the show, he definitely has trouble expressing himself and letting himself be vulnerable when push comes to shove.

The reason the last two seasons have been so good is that Sean [Lowe] and Des did that really well. I don't know if Brooks has it in him to be so open.

Part two of The Bachelorette finale airs Monday on ABC and will be followed by the live After the Final Rose special at 10 p.m.